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The families of flowering plants.                                                                                                                                                                

Viburnaceae Dum.

                        

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~Adoxaceae, Caprifoliaceae, Sambucaceae

Habit and leaf form. Small trees, or shrubs. Mesophytic. Leaves evergreen, or deciduous; small to medium-sized; opposite (mostly), or whorled (rarely); when whorled, i.e. rarely, 3 per whorl; flat; petiolate; simple; epulvinate. Lamina dissected, or entire; if lobed, palmatifid; pinnately veined; cross-venulate. Leaves stipulate, or exstipulate. Stipules when present, intrapetiolar (small, adnate to the petiole); sometimes represented by glands. Lamina margins entire, or serrate, or dentate; flat. Vegetative buds scaly, or not scaly. Leaves without a persistent basal meristem.

Leaf anatomy. Extra-floral nectaries often present (on the petioles). Stomata anomocytic, or paracytic. Hairs present, or absent; eglandular, or eglandular and glandular. Complex hairs present, or absent; peltate, or stellate.

Lamina dorsiventral, or dorsiventral to isobilateral. Minor leaf veins without phloem transfer cells.

Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar (in the few species examined by L.W.). Secondary thickening developing from a conventional cambial ring. Xylem with fibre tracheids. Vessel end-walls scalariform (with many bars). Vessels without vestured pits. Wood parenchyma apotracheal.

Reproductive type, pollination. Plants hermaphrodite, or polygamomonoecious (sometimes varying across the inflorescence?).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, in corymbs, and in panicles. The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary; umbel-like compound corymbs, panicles and thyrses; with involucral bracts, or without involucral bracts; pseudanthial (often with the outer flowers of compact inflorescences larger and sterile), or not pseudanthial. Flowers 1– 2– bracteolate; small to medium-sized; regular; 5 merous; tetracyclic (nearly always), or pentacyclic (V. foetente). Free hypanthium absent.

Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; gamosepalous (reduced); five toothed; regular; persistent; non-accrescent; open in bud; with the median member posterior. Corolla 5; 1 whorled; gamopetalous; imbricate; rotate, or campanulate, or funnel-shaped, or tubular; regular; white (or cream), or pink; deciduous; non-accrescent.

Androecium 5. Androecial members adnate (to the corolla tube); all equal; free of one another; 1 whorled (nearly always), or 2 whorled (V. foetente). Stamens 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits; introrse; bilocular; tetrasporangiate. Endothecium developing fibrous thickenings. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer; of the ‘dicot’ type. Tapetum amoeboid, or glandular. Pollen grains aperturate; 3-celled.

Gynoecium 3 carpelled (with only one fertile locule). Carpels reduced in number relative to the perianth. The pistil 1–3 celled. Gynoecium syncarpous; synstylovarious;inferior. Ovary 1–3 locular. Epigynous disk absent. Gynoecium more or less non-stylate. Stigmas 3; wet type; papillate; Group III type. Placentation of the only fertile locule apical; apical. Ovules in the single cavity 1; 1 per locule (i.e., in the only fertile locule); pendulous; apotropous; with dorsal raphe; anatropous; unitegmic; crassinucellate. Embryo-sac development Adoxa-type (?). Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Endosperm formation cellular. Embryogeny asterad (?).

Fruit fleshy, or non-fleshy (i.e., sometimes more or less dry); indehiscent; a drupe (1– or spuriously 2–3 locular). The drupes with one stone (this usually compressed). Fruit 1 seeded. Seeds endospermic. Endosperm ruminate (rarely), or not ruminate; oily. Cotyledons 2. Embryo achlorophyllous; straight.

Seedling.Germination phanerocotylar.

Physiology, biochemistry. Iridoids detected; ‘Route I’ type (adoxaside). C3. C3 physiology recorded directly in Viburnum.

Geography, cytology. Holarctic, Paleotropical, and Neotropical. Temperate, sub-tropical, and tropical. North temperate, extending to Central America and Java.

Taxonomy.Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Araliiflorae, or Corniflorae; near Araliales (?); Cornales (?). Cronquist’s Subclass Asteridae; Dipsacales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; campanulid; Order Dipsacales (as a synonym of Adoxaceae).

Species about 120. Genera 1; Viburnum.

General remarks. RbcL sequence analyses by Backlund and Bremer (1997) imply close relationship between Adoxa, Sambucus and Viburnum; strongly supporting the taxonomic integrity of Bentham and Hooker’s tribe Caprifoliaceae-Sambuceae (= Adoxaceae sensu lato, e.g. Judd et al. 1984) but suggesting that these genera are relatively distant from Caprifoliaceae. Their true affinities (Cornales or Apiales? — a bone of contention since the nineteenth century) may now have been resolved.

Economic uses, etc. Many ornamentals with showy inflorescences and attractive fruits.

 Illustrations:

  • Technical details: Viburnum.
  • Technical details: Viburnum rugosum (Thonner).
  • Vibernum lantana (B. Ent.). 
  • Viburnum opulus (B. Ent.).
  • Viburnum tinus: Bot. Mag. 2, 1788.
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